In communication systems approved by Third Generation Partnership Project (3GPP), such as Wideband Code Division Multiple Access (WCDMA) (a registered trademark), Long Term Evolution (LTE), and LTE-Advanced (LTE-A), or in communication systems approved by the Institute of Electrical and Electronics Engineers (IEEE), such as Wireless LAN and Worldwide Interoperability for Microwave Access (WiMAX), a base station device (a cell, a first communication device (a communication device that is different from a terminal device), or an eNodeB) and a terminal device (a mobile terminal, a mobile station device, a second communication device (a communication device that is different from the base station device), or user equipment (UE)) each include multiple transmit and receive antennas, and spatial-multiplex a data signal and realize high-speed data communication by using a Multi Input Multi Output (MIMO) technology.
In the communication system, in order to realize the data communication between the base station device and the terminal device, the base station device needs to perform various control processes on the terminal device. For this reason, the base station device notifies the terminal device of control information using a predetermined resource, and thus performs the data communication for downlink and uplink. For example, the base station device notifies the terminal device of resource allocation information, modulation information on and coding information on the data signal, spatial multiplexing information on the data signal, transmit power control information and the like, and thus realizes the data communication.
The communication system supports Time Division Duplex (TDD). LTE that employs a TDD scheme is also referred to as TD-LTE or LTE TDD. TDD is a technology that makes downlink and uplink communication possible in a single frequency band (a carrier frequency or a component carrier) by time-multiplexing an uplink signal and a downlink signal. In LTE, with pre-setting, the downlink and the uplink can be switched on the subframe basis. Moreover, in TDD, a subframe (a downlink subframe, or a subframe reserved for downlink transmission) on which the downlink transmission is possible, a subframe (an uplink subframe, or a subframe reserved for uplink transmission) on which the uplink transmission is possible, and a guard period (GP) are provided, and thus for the downlink transmission and the uplink transmission, a subframe (a special subframe) is defined that is switchable in a time domain (a symbol region). Moreover, in the special subframe, the time domain on which the downlink transmission is possible is referred to as a downlink pilot time slot (DwPTS), and the time domain on which the uplink transmission is possible is referred to as an uplink pilot time slot (UpPTS).
For example, in a case where a subframe i is the downlink subframe, the terminal device can receive the downlink signal that is transmitted from the base station device, and in a case where a subframe j that is different from the subframe i is the uplink subframe, the terminal device can transmit the uplink signal from the terminal device to the base station device. Furthermore, in a case where a subframe k that is different from the subframe i or the subframe j is the special subframe, the downlink signal can be received in the time domain DwPTS of the downlink, and the uplink signal can be transmitted in the time domain UpPTS of the uplink (NPL 1). Furthermore, in order to perform communication in compliance with a TDD scheme in LTE or LTE-A, notification is provided with a special information element (TDD UL/DL configuration (TDD uplink-downlink configuration(s)), TDD configuration (tdd-Config or TDD config), or UL/DL configuration (uplink-downlink configuration(s))). The terminal device regards a certain subframe as any of the uplink subframe, the downlink subframe, and the special subframe, and can perform transmission and reception processing based on information that is notified. Furthermore, a configuration (lengths of the DwPTS, the UpPTS, and a GP within the special subframe) of the special subframe is defined by multiple patterns, and is managed using a table. The multiple patterns are associated with their respective values (indexes) and the value is notified, and thus the terminal device performs processing of the special subframe based on the pattern that is notified.
Furthermore, it is considered that according to traffic (an amount of information, an amount of data, or an amount of communication) of the uplink and traffic (an amount of information, an amount of data, or an amount of communication) of the downlink, a traffic adaptive control technology that changes a ratio between an uplink resource and a downlink resource is applied to TD-LTE. For example, it is considered that a ratio between the downlink subframe and the uplink subframe within 10 subframes is changed dynamically. As this method, a flexible subframe that is adaptively switched between the downlink subframe and the uplink subframe is considered (NPL 2). The base station device can perform reception of the uplink signal or transmission of the downlink signal on the flexible subframe. Furthermore, the terminal device regards the flexible subframe as the downlink subframe and can perform reception processing, as long as the base station device does not instruct the terminal device to transmit the uplink signal on the flexible subframe. Furthermore, in some cases, TDD in which the ratio between the downlink subframe and the uplink subframe, the subframes for the uplink and the downlink, or the TDD UL/DL (re-) configuration is changed dynamically is referred to as dynamic TDD (DTDD).
The communication system is a cellular communication system in which an area is divided in the cellular pattern into multiple areas, each covered by the base station device. Furthermore, a single base station device may manage multiple cells. Furthermore, a single base station device may manage multiple remote radio heads (RRH). Furthermore, a single base station device may manage multiple local areas. Furthermore, a single base station device may manage multiple heterogeneous networks (HetNets). Furthermore, a single base station device may manage multiple low power base station devices (low power nodes (LPNs).
In the communication system, the terminal device can measure a reference signal received power (RSRP) based on a cell-specific reference signal (CRS) (NPL 3).
In the communication system, communication may be performed using a carrier (a component carrier) that is defined in LTE and in which one portion of a physical channel or signal is not mapped. At this point, such a carrier is referred to as a new carrier type (NCT). For example, a cell-specific reference signal, a physical downlink control channel, a synchronization signal (a primary synchronization signal or a secondary synchronization signal) may not be mapped in the new carrier type. Furthermore, it has been considered that a physical channel (a physical discovery channel (PDCH) or a new discovery signal (NDS)) for performing mobility measurement and time/frequency synchronization detection is introduced in a cell for which the new carrier type is set (NPL 4). Moreover, in some cases, the new carrier type is also referred to as an additional carrier type (ACT). Furthermore, in some cases, in contrast to the NCT, a known carrier type is also referred to as a legacy carrier type (LCT).